Plasma processing systems are used in the manufacture and processing of semiconductors, integrated circuits, displays and other devices and materials, to remove material from or to deposit material on a substrate such as a semiconductor substrate. In some instances, these plasma processing systems use electrodes for providing RF energy to a plasma useful for depositing on or removing material from a substrate.
There are several different kinds of plasma processes used during wafer or substrate processing. These processes include, for example: plasma etching, plasma deposition, plasma assisted photoresist stripping and in-situ plasma chamber cleaning.
In plasma reactors, various instruments are used to determine the plasma condition. Some instruments are designed to take measurements directly in the process plasma while other instruments take measurements through appropriate windows. Regardless of the measuring instrument or the specific measuring method used or whether or not windows are utilized, interfaces to the process chamber should remain relatively clean. Otherwise, data gathered by observation or experimentation can be inaccurate.
In a conventional plasma reactor, a formation of a film consisting of adsorbed chemical species present in the processing plasma can adhere to a window. During substrate or wafer processing, the film grows on the window leading to a gradual deterioration of the measurement signal (which can be, for example, an optical signal). This can lead to non-repeatability and non-accuracy of signal measurements made under the same conditions and thus can affect processing tool control systems that base their action on signal input from diagnostic sensors (e.g. optical diagnostics sensors). Therefore, it becomes necessary to clean the window or other interface of accumulated or deposited materials.